H>4 MEMOIRS OF 11 IE NATIONAL ACADEMY OF SCIENCES. 



tluTc i.s some n'a.soii to coiisidfr us sciisorv. This portion of the st'i;iiit'iit is also provided with a 

 peculiar iiiuseulature which enaliles it to act as an adhesive organ of considerable power. 



The t'videncc renders it probable that the laniellated orean upon the inferior labial lobe of 

 the feniaU' is composed of a number of modified cirri. Hetweeii the himelhe are peculiar pits, 

 lined by an ei)itheliiun which seems to be sensory. 



V.w DKK IIoka'en's organ of the male is shown to be the homologue of the inferior labial 

 lobe of the female. Its la'iielhe correspond to the lamelhe and cirri of the inferior laliial lobe. 

 \'ax DKii Ho?:\'En"s organ is largely glandular; its actixity may be periodic. Among the gland 

 cells in all parts of tht> organ are scatteivd great numliers of sensory cells of a peculiar character. 

 These seem to corresjjond to the sensory cells observed upon the inf(>rior la))ial lobe of the 

 female. It is to be noted, however, that in the latter organ the sensory celLs ai"e concentrated, 

 but in the former scattered. The inferior labial lobe is provided with a quite complex special 

 nuisculature. A similar musculature is possessed ))v Van dek H()e\en"s organ. 



The second cirrus of the spadi.v ))ears a set vf glands hithertcj undescribed. The structure 

 of the lai'L;-e slime gland upon the outer surface of the sjjadix sheatli is described. .\ similar 

 gland is found in a less developed condition upon the outei' side of th(> sheath of the antispadix. 

 The spadi.x possesses a powiM'ful nuiscle, extending from its base acro.ss the cephalic sheath. 



The ocular tentacles are proNcn ))y their inner\atit)n to be uuMubcrsof the digital series, modified 

 foi' a sensory function. Fjjon the innei' side of the nerve, within the ocular t(>ntacles, is an acces- 

 sorv nerve composed of many bundles of nei've fillers, which entei' the primary nerve as they pass 

 toward the central ner\'ous system. The ocular tentacles possess '■breaking planes." i. e., planes 

 where the tissues are somewhat discontinuous, and along which the tentacles ))reak with great ease. 



Attention is called to the fact that the position of the organs of the pallial complex of Nautilus 

 has been incorrectly figured and described l)y all authors except Jouliin. The arrangement of 

 these organs ditiers from that found in the Di))ranchiata, and approaches that found in many 

 Gastropoda. The gills, anus, preanal and interbranchial papilhe. ])ericardial and renal pores, 

 and the nidamental gland are situated u))on the inner surface of the mantle. The paired repro- 

 ductive oririces are situated upon the body wall within the mantle cavity. 



There does not yet seem to be sutBcient evidence to warrant our calling certain papilla; near 

 the bases of the gills osji/u't/'f/c Both dissections and serial sections of the papillw in ciue.stion 

 have failed to show the s|)ecial imier\ation required; other observers also seem to l)e a little less 

 than sure of the presence of special nerves to these papilla?. 



The funnel is composed of two essentially difl'erent portions, the anterior part being tibrous, 

 the posterior portion nuiscular. The crura of the funnel are so formed that they can, liy a 

 fanning motion, cause respiratory currents through the mantle chamber, and possiliiy cui'rents 

 strong enougli for tlie pi'ogr(>ssion of the animal. 



The visceral portion of the body wall is thin and non-muscular. It contains a nervous plexus. 

 It is attached to the shell by three aponeurotic bands proceeding from the ends of the shell 

 nmscles. The dorsal and posterior ventral bands limit the septum-forming portion of the body 

 wall. A sharp ))ackward pioj(>ction vf the dorsal aponeurotic band corresponds to a depression 

 in the face of each septum in tiie younger hiilf or two-thirds of the shell. 



Aside fi'om minor additions in the descrijition of th(> anatomy of the digestive tract as a whole, 

 the muscles of the buccal mass are described and tigured. They are found to form a quite highly 

 deveh)ped .system. 



The renal organs are found within the mantle and in the reverse position from that described 

 by earlier authors. 



Willey's sketches and my own dissections have lieen conibincd to form a nearly complete 

 account of the arterial circulation. 



Some previously undesci-ibed nerves have been followed to their terminations, especially the 

 nerves of the ocular tentacles, of Van per Hoeven's organ, and of the spadix and antisj)adix. 



The ocular nerves ar(> bi-anches of a nerve supplying digital tentacles as well. The nerves of 

 Van dek Hoeven's organ corresjiond to the lun-ves of the inferior labial lobe in all particulars. 

 The, otocvstic nerve arises from the cen'bral ganglion. 



